LISTOWEL, Ont. - Two firefighters were killed in the line of duty in southwestern Ontario Thursday.

Raymond Walter, 30, and Kenneth Rea, 55, died when the roof of burning dollar-store collapsed on them in Listowel, Ont., about 160 kilometres west of Toronto, QMI Agency has confirmed.

Walter was from Listowel and Rea hailed from Atwood, Ont. Both men were married, police said.

"The mood is complete sadness and disbelief," said Const. Kees Wijnands. "It seems kind of surreal how black the smoke was when the fire started and how quiet it is right now."

While they were battling the blaze, the roof of the Dollar Shop collapsed, trapping them. Their bodies have not yet been recovered from the building, which was still smouldering Thursday night.

"You could see flames all along the west side and flames were shooting out of the roof," said Kelly Irwin, who works in the building next door and was just going out for lunch when she saw thick, black smoke. "I heard a series of pops, like small explosions. I saw about five firefighters go in the front of the building and I didn't see any come out."

A number of firefighters were in the building when the roof collapsed, but only two died.

"They put their own lives at risk in order to protect their communities, just as firefighters do every day across Ontario," he said in a statement issued late Thursday night.

"Our volunteer firefighters take time away from their families to keep us safe. We rely on their selflessness, and today's tragedy is a solemn reminder that we must never take their sacrifices for granted."

Sgt. Dave Rektor said it's still unclear what caused the fire. The Ontario Fire Marshal's office has taken control of the scene, and the investigation is ongoing.

"It's tragic," said Jim Holmes, the head of the London Professional Firefighters Association, when told of the news. "They sacrificed their lives for the safety of their community."

The news hits home for Ernie Hardeman, member of the provincial parliament for Oxford County, who spent 25 years as a volunteer firefighter with Southwest Oxford.

"You have a lot of events, but it never really hits home that something like that can happen, particularly in your own community," said Hardeman. "It's just hard to imagine what they must be going through and the pain of all the 'what-ifs.'"